A packet transfer apparatus connects two networks of different protocols. The packet transfer apparatus, connected to a first communication network and a second communication network, performs the steps of: storing first destination correspondence information; receiving a packet of the first communication protocol; based on the first destination correspondence information, determining destination information of a packet of the second communication protocol corresponding to destination information of the received packet of the first communication protocol; generating the header of the packet of the second communication protocol, based on the determined destination information of the packet of the second communication protocol; converting the received one or more packets of the first communication protocol into one or more packets of the third communication protocol; and adding the generated header of the packet of the second communication protocol to the packets of the third communication protocol.